Normal infants display a number of immaturities of binocular vision that resemble in many ways the pathological states found in patients with strabismus and/or amblyopia. Both groups demonstrate direction asymmetries of motion VEPs and of eye movements under monocular viewing conditions. Interruptions of binocularity during early postnatal development prevent normal development of these direction asymmetries and successful treatment can restore more normal function. The purpose of the proposed work is to examine the relationships among various forms of binocularity and the monocular direction asymmetry as they develop in normal and pathological visual systems. Aim I will examine the nature of spatio-temporal interactions in developing motion systems using the VEP direction asymmetries to map the complete developmental sequence of direction selectivity in normal infants. Aim 2 will determine if binocular motion mechanisms have the same developmental sequence as stereopsis using a sweep VEP technique to measure stereopsis and binocularity in the motion system simultaneously. Aim 3 will study the developmental sequence of normal suppressive binocular interaction. Dichoptic masking functions will be measured using a sweep VEP technique that will at the same time quantify the magnitude of the developmental direction asymmetry. Aim 4 will determine how motion processing asymmetries change as a function of the accuracy of alignment after treatment for strabismus. Plastic changes in monocular VEP direction asymmetries will be studies using VEP techniques in patients undergoing three different esotropia treatment regimes; conventional surgery at age 12-18 months, Botulinum Toxin injection between 4 and 12 months and conventional surgery at age 4 years. The dynamics of plastic changes will be studied as a function of the accuracy of alignment and the extent to which normal motion processing can be restored after treatment will be determined.